I have noted that many sellers are for too optimistic about their claims for many vintage drivers and  complete speakers.
    Generally vintage drivers are of use to restorers and collectors.  Be very suspicious when a seller says they sound great.  Compared to modern drivers they will usually sound awful.  And the same can generally be said of complete speakers.
    Remember that the Thiel Small parameters were not developed until 1974.  Prior to that no one had a clue how to align the driver to the box, or what parameters were even desirable in a driver.  Generally you should not pay more than a few dollars for drivers and speakers from this era.
    There are a few exceptions.  The Quad 57 was the worlds first tonally accurate speaker, and is still a good listen if you can find one in good shape.  Remember they are frail and do not play loud!.  If you play them too loud you will put a hole in the membrane and the speaker will buzz.
    The Jordan Watts module introduced in 1961, was the first really accurate moving coil driver. It is still a good listen, but again frail and prone to cone voice coil seperation.
     Lowther drivers especially the PM 6 have a sound better than most other drivers from the early days of audio.  However they are a bit shouty due to a 2000 to 2500 Hz peak.
    The KEF B 130 bass driver is still useful, and has an excellent bass response.  The Thiel Small parameters are well known and consistent.  The driver will go lower than any other driver in a relatively small closed or vented box, and they are excellent for transmission line loading.  However, the Polystyrene cones resonate violently at 900 Hz, and so high order crossovers are essential, which adds to complexity, cost and parts count in the crossover.
    Altec Voice of the Theater, and comparable products from JBL and Electrovoice are aslo some what of an exception, when sound for large rooms are considered.  However you can still get better results with modern systems.
     So the bottom line is don't be tempted to give more than a few dollars for most vintage drivers and speaker systems.  Generally by all means collect if you want a museum.  Just don't kid yourself you are buying the last word in audio.  You won't be.
     I have done my best to point out the exceptions, but the list is may not be totally inclusive.  However I have been designing and building speakers for fifty years, and have experince of a wide range of drivers and speakers.
     Mark Carter MD.